Microfabrication by lithography using a photoresist has hitherto been carried out in the manufacture of semiconductor devices. Such microfabrication is a process that entails forming a thin film of photoresist on a semiconductor substrate such as a silicon wafer, exposing the photoresist from above to actinic light such as ultraviolet light through a mask on which the pattern for a semiconductor device has been written, developing the exposed photoresist so as to forma photoresist pattern, and etching the substrate while using the photoresist pattern as a protective layer so as to form on the substrate surface very small features which correspond to the pattern. In recent years, with the advances being made toward higher levels of integration in semiconductor devices, there has been a trend toward the use of shorter wavelength actinic light, specifically from a KrF excimer laser (248 nm) to an ArF excimer laser (193 nm). Along with this, the influence of actinic light reflected from the semiconductor substrate has become a major problem. To resolve this problem, methods for providing an anti-reflective coating (bottom anti-reflective coating) between the photoresist and the substrate are being widely investigated. Owing to their ease of use, numerous investigations are being carried out on organic anti-reflective coatings composed of, e.g., polymers having light-absorbing groups, as such anti-reflective coatings. Examples include acrylic resin-based anti-reflective coatings having a hydroxyl group (a crosslinking reaction group) and a light-absorbing group on the same molecule, and novolak resin-based anti-reflective coatings having a hydroxyl group (crosslinking reaction group) and a light-absorbing group on the same molecule.
The properties required of anti-reflective coatings include a large absorbance with respect to light and radiation, the absence of intermixing with photoresist (insolubility in a photoresist solution), no diffusion of low-molecular-weight substances from the anti-reflective coating to the overlying photoresist layer during heating and baking, and a high dry etch rate compared with the photoresist.
Recently, in order to resolve the growing problem of wire delay associated with advances toward a finer pattern rule in semiconductor devices, investigations involving the use of copper as the interconnect material have been carried out. Together with this, the dual damascene process is being investigated as a method of forming interconnects on a semiconductor substrate. In the dual damascene process, an anti-reflective coating is formed on a substrate in which via holes have been formed and which has a large aspect ratio. Hence, the anti-reflective coating used in this process is required to have, for example, burial properties that enable the holes to be filled without leaving any gaps, and planarizing properties such that a flat film is formed on the substrate surface.
A film known as a hard mask which includes silicon and metallic elements such as titanium is used as the underlayer film between a semiconductor substrate and a photoresist (see, for example, Patent Document 1). Because of major differences between the constituent ingredients in the resist and the hard mask, their rates of removal by dry etching are strongly dependent on the gas species used in dry etching. Through suitable selection of the gas species, it is possible to remove the hard mask by dry etching without a large accompanying decrease in the photoresist film thickness. Hence, in semiconductor device fabrication today, to achieve various effects, including an anti-reflection effect, it has become common practice to place a resist underlayer film between the semiconductor substrate and the photoresist. Although investigations have hitherto been carried out on resist underlayer film compositions, owing in part to the multiplicity of the properties required, there exists a need for the development of novel resist underlayer film materials.
Compositions and patterning methods which use compounds having silicon-silicon bonds are known (see, for example, Patent Document 2).
Silicon-containing resist overcoat film-forming compositions which contain sulfonamide groups have been disclosed (see, for example, Patent Document 3).
In addition, silicon-containing resist underlayer film-forming compositions which contain sulfonamide groups have been disclosed (see, for example, Patent Document 4).    Patent Document 1: Japanese Patent Application Publication No. H11-258813    Patent Document 2: Japanese Patent Application Publication No. H10-209134    Patent Document 3: Japanese Translation of PCT Application No. 2008-519297    Patent Document 4: Japanese Patent Application Publication No. 2009-244722